The present invention relates to a system for connecting two tubes together end to end, the system comprising a clamping collar having a clamping band suitable for being tightened around the abutted ends of two tubes.
More precisely, the invention relates to a clamping system of the above-specified type that is suitable for being pre-attached at the end of the first tube prior to abutting it with the second tube and tightening the band.
A clamping system of this type is known from Documents EP 1 451 498 and EP 2 598 785, for the particular situation in which the tubes have bearing surfaces and the inside periphery of the collar defines a trough receiving those surfaces.
In the above-mentioned patent documents, the clamping system includes pre-attachment means that, in the non-clamped state of the collar, serve to secure the collar to the first tube before it is coupled with the second tube. The collar is thus, so to speak, left on standby at the end of the first tube in order to facilitate coupling together the first and second tubes, and then clamp the two coupled-together tubes.
The clamping systems described in the above-mentioned patent documents present a washer that is secured to the collar, which washer has tabs or the like for pre-attachment of the assembly comprising the collar and its washer, with the first tube.
Systems of that type give satisfaction, but they require the use of a washer. The washer may have functions other than that of contributing to pre-attachment, in particular it may contribute to sealing the coupling between the two tubes once they have been clamped together. Nevertheless, in certain systems, it is possible to use a sealing washer that is of simpler shape, or indeed to avoid using any such washer, in particular if the tubes are of a shape that itself enhances sealing where the tubes are coupled together, or if the level of sealing required is low.
Document EP 1 840 439 discloses a system for connecting two tubes together end to end, the system comprising a clamping collar having a clamping band suitable for being tightened around the abutting ends of the two tubes, the collar having a retaining tab that presents a fastener portion whereby said retaining tab is fastened to the band of the collar and that extends substantially axially towards an attachment portion of said retaining tab whereby said retaining tab is suitable for being attached to the first tube in the vicinity of its first end.
According to Document EP 1 840 439, before the collar is tightened, that tab can be attached to one of the tubes, e.g. by welding, in order to put the system on standby on the tube, i.e. in a pre-attached situation, prior to abutting the tube with the other tube and then tightening the collar.
Nevertheless, that system raises a problem of effectiveness. Specifically, in order to position the pre-attached system correctly, it is necessary for the tab to be sufficiently rigid. Unfortunately, such rigidity prevents the retaining tab from being deformed easily while tightening the collar, thereby complicating the tightening operation and, in the extreme, that can be detrimental to the effectiveness of the clamping.
In contrast, if the tab is very flexible, so that it can be easily deformed during tightening, it runs the risk of not holding the system correctly in the pre-attached position, thereby complicating the operations of abutting the tubes and of tightening, and that can likewise be detrimental to the effectiveness of the clamping. The present invention seeks to propose a system of the above-specified type for connecting together two tubes, which system is substantially free of the above-mentioned drawbacks.